In the manufacture of a semiconductor device a layer of conductive material (e.g., metal) may be deposited over an underlying structure. When portions of the layer of conductive material are later etched away there are usually some residual stringers of conductive material that are not removed from the features of the underlying structure. The stringers of conductive material usually remain at the corners of vertical feature edges. An excessive overetch process is usually required in order to remove the stringers of conductive material from the corners of the vertical feature edges.
For example, consider the prior art semiconductor device 100 shown in FIG. 1. The semiconductor device 100 comprises a silicon or silicon dioxide substrate 110, a thin film resistor (TFR) 120, a titanium tungsten (TiW) protective layer 130, and a patterned photoresist layer 140.
When a prior art plasma etch process is applied to the semiconductor device 100, the plasma etch process etches away portions of the photoresist layer 140 and portions of the titanium tungsten (TiW) protective layer 130. The result is shown in FIG. 2 where the etched semiconductor device is designated with reference numeral 200.
As shown in FIG. 2, the exposed flat surfaces 210 of the silicon substrate 110 and the vertical edges 220 of the titanium tungsten (TiW) protective layer 130 form corners at an angle of approximately ninety degrees (i.e., a right angle). Assume that the photoresist layer 140 is then removed and a conductive layer (not shown) is deposited over the semiconductor device. When the conductive layer is subsequently etched away the conductive layer leaves stringers of conductive material 310 lodged in the corners between the vertical edges 220 of the titanium tungsten (TiW) protective layer 130 and the flat surfaces 210 of the silicon substrate 110. The resulting structure 300 is shown in FIG. 3.
In order to remove the stringers 310 of conductive material at the feature edges it is necessary to continue to apply the etch process to the conductive material. The continuation of the etch process produces an excessive overetch that may produce other undesirable effects in the structure of the semiconductor device. For example, excessive loss of the titanium tungsten (TiW) protective layer 130 may occur to the point of exposing the thin film resistor (TFR) 120 to the plasma etch process. Such exposure would destroy the thin film resistor (TFR) 120.
For this reason the prior art approach described above is not desirable because it requires an excessive overetch process to be employed. Therefore, it would be advantageous to have an efficient system and method that can reduce the overetch process for the conductive material that is required to remove stringers of conductive material from portions of a semiconductor device.
Before undertaking the Detailed Description of the Invention below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like.
Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior uses, as well as to future uses, of such defined words and phrases.